Bisphenol-A polycarbonate polymers are excellent molding materials as products made therefrom have relatively high impact strength, toughness, high transparency, wide temperature limits (high impact resistance below -60.degree. C. and a UL thermal endurance rating of 115.degree. C. with impact), good dimensional stability, high creep resistance and electrical properties which qualify it as sole support for current carrying parts.
Bisphenol-A polycarbonates are, however, very difficult to fabricate from melts for the reason that melts thereof have exceptionally high viscosities. Attempts to overcome this difficulty by the incorporation into the polycarbonate of materials known to reduce the viscosity of other resins have very generally been unseccesful. Many standard viscosity control agents appear to have little or no effect on the viscosity of polycarbonates. Some compounds, which are conventionally employed to improve the workability of polymers, produce an embrittling effect on polycarbonates when they are mixed therewith and the mixture is subjected to elevated temperatures as in molding. Still other materials, while satisfactory stiffness modifying agents for other plastics, are too volatile to be incorporated into polycarbonates since polycarbonates have much higher melting points than many other thermoplastics.
It has now been found that the incorporation of a relatively minor amount of an oligomeric ester plasticizer, such as, an alcohol terminated oligomeric ester of neopentyl glycol (2,2-dimethyl-1,3-propane-diol) and adipic acid in admixture with a minor amount of an olefinic impact modifier, such as, for example, polyolefins, olefin based copolymers and olefin based terpolymers, such as, ethylene-propylene copolymers, ethylene-butadiene copolymers, propylene-butadiene copolymers, ethylene-propylene-butadiene terpolymers, ethylene-acrylic acid copolymers, propylene-acrylic acid copolymers, ethylene-ethyl acrylate copolymers, ethylene-vinyl acetate copolymers and ethylene-propylene-acrylic acid terpolymers; or in admixture with an amount of an acrylic rubber impact modifier, such as, for example, methyl methacrylate-butadiene-styrene copolymers, methyl methacrylate-acrylonitrile-butadiene-styrene copolymers, and acrylonitrile-butadiene-styrene copolymers; into a bisphenol-A polycarbonate will significantly improve the processability of the resultant polycarbonate molding material and, at the same time, provide a material having improved notched Izod impact strength characteristics.